Ethernet Frame

Getting Connected

Larry L. Peterson , Bruce S. Davie , in Computer Networks (Fifth Edition), 2012

Frame Format

Each Ethernet frame is divers past the format given in Figure 2.25. six The 64-bit preamble allows the receiver to synchronize with the signal; it is a sequence of alternating 0s and 1s. Both the source and destination hosts are identified with a 48-flake address. The packet type field serves as the demultiplexing central; it identifies to which of possibly many higher-level protocols this frame should be delivered. Each frame contains up to 1500 bytes of information. Minimally, a frame must comprise at least 46 bytes of data, even if this means the host has to pad the frame earlier transmitting it. The reason for this minimum frame size is that the frame must be long enough to detect a standoff; we hash out this more below. Finally, each frame includes a 32-bit CRC. Like the HDLC protocol described in Department two.3.2, the Ethernet is a chip-oriented framing protocol. Note that from the host's perspective, an Ethernet frame has a 14-byte header: two 6-byte addresses and a 2-byte blazon field. The sending adaptor attaches the preamble and CRC earlier transmitting, and the receiving adaptor removes them.

Figure 2.25. Ethernet frame format.

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Introduction to Sniffer Pro

Robert J. Shimonski , ... Yuri Gordienko , in Sniffer Pro Network Optimization and Troubleshooting Handbook, 2002

IPX/SPX

Internetwork Bundle Substitution/Sequenced Bundle Exchange (IPX/SPX) is a Novell communications protocol suite derived from the Xerox Network System (XNS) protocol. Figure 1.8 shows how the IPX/SPX protocol stack maps confronting the OSI reference model.

Figure 1.8. Layers of the IPX/SPX Protocol Stack

IPX is a connectionless Layer 3 network protocol. Although multiple Novell protocols operate at Layer 4, SPX is the most common one. SPX, a reliable, connectedness-oriented protocol, was derived from the XNS Sequenced Parcel Protocol (SPP). Network Core Protocol (NCP) provides interaction between clients and servers by defining connexion control and service asking/reply. Service Advertisement Protocol (SAP) allows servers to advertise their addresses and the services they provide.

Figure 1.ix shows an instance of an IPX packet captured with Sniffer Pro.

Figure ane.9. IPX Parcel Captured on Sniffer Pro

IPX Addressin

An IPX address consists of ii parts: the network number and the node number. IPX addresses are lxxx $.25 long, with 32 bits for the network number and 48 bits for the node number. IPX simplifies mapping between Layer 3 and Layer 2 addresses, using the Layer 2 address every bit the host portion of the Layer iii address. This eliminates the need for an address resolution protocol such every bit Address Resolution Protocol (ARP) for IP. IPX addresses are more often than not written as hexadecimal digits in the network.node format.

Unlike IP, IPX has no concept of subnetworking. The IPX network number is manually assigned and must be unique for each network segment. Each node number on a given IPX network segment must exist unique.

NOTE

IPX supports multiple Ethernet frame types: Ethernet II, IEEE 802.3, IEEE 802.iii SNAP, and Novell 802.3 RAW. (Frame types are discussed in detail later in the chapter.) It is possible to use multiple encapsulation types on a single network segment as long as a unique network number is assigned to each encapsulation type. It is important to note that hosts that use different encapsulation types will non be able to directly communicate with each other.

Node numbers do not have to exist unique beyond networks because the network number and node number are used together to identify a detail host.

Internal Network Numbering and Server Addresses

IPX contains two types of network numbers: internal network numbers and network numbers assigned to local area network (LAN) and some wide area network (WAN) interfaces (sometimes called "external" network numbers). An internal network number identifies an extension of your internal network, sometimes referred to as a virtual network segment. For example, a router will add together an additional hop en route to a workstation if you have configured your internal network number on a workstation running IPX.

The apply of an internal network number allows for improved mistake tolerance on the network. IPX resources are referenced past SAP names that point to an IPX address. Using an internal network number as a part of the SAP accost means that in the event of a failure of a particular network segment, merely the IPX route, not the SAP tables, volition take to be adapted to an alternate path.

The internal network number is an eight-digit hexadecimal number betwixt 0x1 and 0xFFFFFFFE and must be unique cross the entire IPX network. Although 0xFFFFFFFE was originally immune for utilize every bit an address, this changed after the introduction of Network Link Services Protocol (NLSP). Both NLSP and IPX RIP have been modified since then to recognize 0xFFFFFFFE as the default route. When you use the internal network number, the host portion of the IPX address is set up to ane.

How to Translate an IPX Accost

Figure ane.ten describes an IPX address in more than detail. The first 32 $.25 of the accost are the network number and are configured by the network administrator. This number must exist a hex value betwixt 0x00000001 and 0xFFFFFFFD. In this case, the network number is configured equally the hex value 0xBEEF. The last 48 $.25 of the address are the same every bit the Media Admission Control (MAC) address and come from the NIC. In this case, the MAC address of the NIC is 00-xx-E0-88-80-74, which is likewise used equally the IPX node number.

Figure 1.10. Instance of an IPX Address

NOTE

The default behavior for an IPX node is to adopt the NIC's MAC address as the IPX node number. Nonetheless, a network ambassador can choose to override this behavior past statically assigning an IPX node number to a system. Be careful, however! If the assigned node number is non unique on the network, you lot may end upward with two systems on the network with the same IPX node number. This can cause serious network problems. You can use the Sniffer Pro software to find duplicate node numbers assigned on a network.

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Data Center Networking Standards

Gary Lee , in Cloud Networking, 2014

Priority-based period control

PFC is very similar to priority link-level period command that we described in Chapter 3 and is used to provide lossless operation for certain types of information eye traffic, such as storage. Effigy 5.3 shows an example implementation of PFC between switch stages.

Figure five.3. Priority-based flow control cake diagram.

Up to 8 priority levels are supported with PFC, but typical implementations may apply only two or three. In this example, the 2nd switch stage uses traffic-class-based retentivity partitions with programmable watermarks. If an allocated memory partition starts to fill up up and a watermark is crossed, a priority flow control message is generated and sent to the transmitting switch, which and then stops sending frames assigned to that item traffic class for a specified suspension time included in the frame. Transmission is resumed when the suspension time expires. This ensures that other noncongested traffic is non paused and, therefore, remains unaffected. Proceed in mind that a single retentivity partition in a shared memory switch may exist receiving data from multiple switch ports and, therefore, will need to send PFC messages to all of these ports once a watermark level is exceeded.

Priority flow control evolved from the IEEE 802.3x break frame which was designed to break all traffic if a receiving switch global memory started to fill up. The IEEE 802.1Qbb PFC frame format is shown in Figure 5.4.

Figure v.4. PFC frame format.

This is effectively a standard Ethernet frame but with some predefined fields and a special payload. The of import fields are defined as follows:

•

Destination MAC address: This field is ready to a particularly reserved multicast address of 0x0180C2000001 in order to identify the frame as an IEEE 802.1Qbb PFC frame.

•

Source MAC address: This is gear up to the MAC address of the sending device.

•

Ethernet type: This is ready to 0x8808 for this blazon of frame.

•

Class-enable $.25: These bits represent traffic classes 0–seven. If a bit is set loftier, pause is enabled for that grade.

•

Grade time fields: For each course-enable bit that is set, these 16-bit values specify the length of time to enable pausing of the particular traffic form. A value of zippo tells the sender to united nations-suspension that item traffic grade.

The method in which these values are generated is somewhat vendor and implementation specific. For instance, one switch may support eight traffic classes, while the other supports but ii. In improver, the pause time and watermark settings depend on the round-trip flow control delay time as described in Chapter 3. The watermark settings must leave plenty room in the memory sectionalisation so that frames in flight earlier intermission is enabled will still have available memory space. Pause filibuster times must be long enough so that memory usage levels drop sufficiently before new frames showtime to arrive. For instance, if jumbo frames are existence used, or at that place are long distances between link partners, the watermark setting volition demand to be lowered and pause times will need to exist increased.

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Transmission Control Protocol/Net Protocol Bundle Analysis

Pramod Pandya , in Computer and Information Security Handbook (Third Edition), 2013

Address Resolution Protocol

The IP protocol is capable of routing an IP datagram within the aforementioned IP segment (network address), or else it would demand a router to route the datagram to a dissimilar IP segment (network address). The IP protocol uses the IP address specified in the destination IP field and the subnet mask to extract the destination IP network address to which the datagram must be routed. The IP protocol looks upwards in its routing table to determine whether the destination network is directly attainable by the node or whether information technology needs the router to route the datagram to the destination network. The reader needs to exist reminded that the Ethernet protocol on the host node needs the MAC address of the destination node to prepare the Ethernet frame. The host node has a routing table with IP addresses mapped to Ethernet addresses, known as ARP cache. If the ARP cache does not accept the MAC address mapped to its corresponding IP address entry, an ARP request is generated by the host node to discover the MAC address corresponding to its IP address. If the destination node is on the same network, this is resolved by the destination node upon its ARP respond, and the destination MAC address corresponding to destination IP address is resolved. If the datagram needs to be routed out of the network address, the IP on the host node generates an ARP request to resolve the IP accost to the MAC address of the Ethernet interface on the router to which the network segment connects. In such a case, the MAC address of the router interface is used as an intermediate MAC address. Once the IP address to the MAC address is resolved, the Ethernet protocol can build the Ethernet frame side by side and encapsulate the IP datagram. An ARP parcel is directly encapsulated (bypassing IP datagram) into an Ethernet frame, every bit shown in Fig. e73.6.

Figure e73.6. Encapsulation of an Address Resolution Protocol (ARP) package in an Ethernet frame. CRC, Cyclic Redundancy Check; SFD, Start Frame Delimiter.

The destination address in the Ethernet frame is all 1s, indicating that it is a circulate address. Fig. e73.7 illustrates the ARP packet format. Each field is described as follows:

Figure e73.7. Address Resolution Protocol (ARP) packet.
•

Hardware blazon: 16-bit field that defines the type of the network on which ARP is running. Ethernet is given type 1

•

Protocol type: sixteen-bit field defines the protocol. For IPv4, the value of this field is 0   ×   800

•

Hardware length: viii-bit field that defines the length of the physical address, which is half dozen   bytes for the Ethernet address

•

Protocol length: 8-flake field that defines the length of the logical address, which is 4   bytes for the IPv4 protocol

•

Operation: 16-bit field defining the type of bundle. Two parcel types are ARP request (i) and ARP answer (2)

•

Sender hardware address: The physical accost of the sender node

•

Sender protocol accost: The logical address of the sender node

•

Target hardware address: A field set up to all 0s for an ARP request

•

Target protocol address: A field set up to the IP address of the target node

Fig. e73.8 is a screen capture of an Ethernet frame using a sniffer program. Ping is executed from a node with IP accost 192.168.ane.3 to a node with IP address 192.168.ane.iv. The screen capture is divided into iii panels. The upper panel displays half-dozen columns of information. Packet half dozen is highlighted in the upper panel, showing that an ARP request was generated with the source address 00,045AA29675 and destination address FFFFFFFFFFFF, which is a broadcast address. Under the description column in the upper panel, the node with IP address 192.168.1.3 is broadcasting on the network to find the MAC accost corresponding to IP address 192.1681.4. The Ethernet frame in the lower-right panel shows a destination address of FFFFFFFFFFFF, which is a broadcast accost.

Figure e73.eight. Captured Ethernet frame.

Fig. e73.ix represents the contents of the Ethernet frame and the ARP packet it encapsulates. The contents of the ARP packet displays the IP and MAC addresses of the sender'southward node. The target hardware address is sixteen zeros and the target IP address is 192.168.1.iv.

Figure e73.9. Contents of an Address Resolution Protocol (ARP) packet.

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Industrial Network Protocols

Eric Knapp , in Industrial Network Security, 2011

Ethernet/IP

Ethernet/IP uses standard Ethernet frames (ethertype 0x80E1) in conjunction with the Common Industrial Protocol (CIP) suite to communicate with nodes. Communication is typically customer/server, although an "implicit" way is supported to handle real-time requirements. Implicit style uses connectionless transport—specifically the User Datagram Protocol (UDP) and multicast transmissions—to minimize latency and jitter.

Note

The "IP" in Ethernet/IP derives from "Industrial Protocol" and non "Internet Protocol," because of the use of the Common Industrial Protocol (CIP). Similarly, the acronym "CIP" meaning "Common Industrial Protocol" should not exist confused with "Critical Infrastructure Protection" of NERC CIP.

The CIP uses object models to define the diverse qualities of a device. There are three types of objects: Required Objects, which define attributes such as device identifiers, routing identifiers, and other attributes of a device such as the manufacturer, serial number, date of manufacture, etc.; Application Objects, which define input and output profiles for devices; and Vendor-specific Objects, which enable vendors to add proprietary objects to a device. Objects (other than vendor-specific objects) are standardized past device type and role, to facilitate interoperability: if ane brand of pump is exchanged for another brand, for example, the application objects will remain uniform, eliminating the need to build custom drivers. The broad adoption and standardization of CIP has resulted in an extensive library of device models, which can facilitate interoperability but can also assist in control network scanning and enumeration (see Chapter 6, "Vulnerability and Risk Assessment").

While the Required Objects provide a common and complete set of identifying values, the Awarding Objects incorporate a mutual and complete suite of services for command, configuration, and data collection that includes both implicit (command) and explicit (information) messaging. 28

Security Concerns

Ethernet/IP is a existent-time Ethernet protocol, and as such it is susceptible to whatever of the vulnerabilities of Ethernet. Ethernet/IP over UDP is transaction-less and so there is no inherent network-layer machinery for reliability, ordering, or data integrity checks. The CIP also introduces some specific security concerns, due to its well-divers object model.

The post-obit concerns are specific to Ethernet/IP:

•

The CIP does not define any explicit or implicit mechanisms for security.

•

The use of mutual Required Objects for device identification tin facilitate device identification and enumeration, facilitating an attack.

•

The use of common Application Objects for device information exchange and command tin enable broader industrial attacks, able to dispense a broad range of industrial devices.

•

Ethernet/IP'southward use of UDP and Multicast traffic—both of which lack transmission control—for real-time transmissions facilitate the injection of spoofed traffic or (in the case of multicast traffic) the manipulation of the manual path using injected IGMP controls.

Security Recommendations

Because Ethernet/IP is a real-time Ethernet protocol using UDP and IGMP, it is necessary to provide Ethernet and IP-based security at the perimeter of any Ethernet/IP network. It is also recommended that passive network monitoring exist used to ensure the integrity of the Ethernet/IP network, ensuring that the Ethernet/IP protocol is only beingness used by explicitly identified devices and that no Ethernet/IP traffic is originating from an unauthorized, outside source. This can be accomplished using a SCADA-IDS/IPS or other network monitoring device capable of detecting and interpreting the Ethernet/IP protocol.

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Cablevision Networking Protocols

Walter Ciciora , ... Michael Adams , in Modern Cable Television Technology (Second Edition), 2004

Ethernet Frames

Figure 5.13 shows the makeup of an Ethernet frame. A frame holds one packet of data. The outset 8 bytes are the preamble. Some Ethernet systems don't transmit continuously, and so the preamble is used to synchronize a receive clock before information is transmitted. In other Ethernet systems, data transmission is continuous, but the preamble has been retained to keep the frame structure.

Figure 5.xiii. Ethernet frame.

The next vi bytes are the destination address — the MAC accost of the intended recipient of the packet. Side by side is the source address, the MAC address of the sender. This is needed to allow the recipient to answer to the source and also to allow switches to learn the MAC address on each port, for efficient bundle routing. Following the address fields is the type/length field, which is used for several purposes. It can identify the higher-layer network protocol carried in the data field, as described next. Information technology as well identifies the length of the packet. Unlike ATM cells, Ethernet packets are of variable length, and then something must tell the receiver when a parcel ends.

Next is the data, the affair nosotros desire to transmit. It may take headers for higher-layer protocols embedded in it. The length of the information is betwixt 46 and 1,500 bytes. Post-obit the data is the frame check sequence, a cyclical redundancy code used for mistake checking but not correction. Error checking is described briefly in Chapter 3.

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Network Link Technologies

Walter Goralski , in The Illustrated Network (2nd Edition), 2017

The IEEE 802.11 Frame

Although the IEEE 802.11 frame shares a lot with the Ethernet frame (which is one reason some packet sniffers can parse wireless frames as if they were Ethernet), there are a number of unique fields in 802.11. There are nine main fields, and the frame control (FC) field has 10 fields. The nine major fields of the IEEE 802.11 MAC frame are shown in Figure 3.xiv. The but fields in the two FC bytes that we will talk about are the From DS and To DS fields. (In some cases, the first three fields of the 802.11 MAC frame, the version, type, and subtype, are presented separately from the frame command flags, which are all $.25.)

Figure three.14. IEEE 802.11 frame structure. Note the potential number of address fields (four) in contrast to the two used in Ethernet II frames.

Frame control (FC)—This field is two bytes long and contains, among other things, two important flag bits: To DS (distribution organisation) and From DS.

Duration—This byte gives the duration of the transmission in all frame types except ane. In i control frame, this "D" byte gives the ID of the frame.

Addresses—There are four possible address fields, each 6 bytes long and structured the same as Ethernet MAC addresses. The quaternary field is but present when multiple APs are in utilise in an ESS. The meaning of each address field depends on the value of the DS flags in the FC field, discussed later.

Sequence control—This 2-byte field gives the sequence number of the frame and is used in catamenia command.

Payload—This field tin can be from 0 to 2312 bytes long. Ordinarily it is fewer than 1500 bytes and holds an IP packet, but in that location are other types of payloads. The precise type and subtype of the content is determined by the content of the FC field.

CRC—The frame cyclical redundancy check is a iv-byte CRC-32, used to determine the nature of the acknowledgement sent.

Why does the wireless frame demand to define four address fields? Mainly considering the arrangements of wireless stations can be complicated. Is in that location an AP in the BSS? Is there more i AP? What blazon of frame is being sent? Data? Control? Management? The number of address fields present, and what they represent, depend on the answers to these questions.

How do receivers know exactly how many addresses are used and what they represent? That'south where the two DS flags in the FC field come in. The pregnant of the address fields (and possible presence of the Address 4 field) depends on the values of these two $.25. Actually, there are five types of MAC addresses used in wireless LANs:

BSSID—This is ordinarily the MAC address of the AP, but information technology is generated randomly in an IBSS or advertizing hoc network.

Transmitter Address (TA)—The TA is the MAC address of the individual station that has just sent the frame.

Receiver Address (RA)—The RA is the MAC address of the immediate receiver of the frame. This can be a group or broadcast accost.

Source Accost (SA)—The SA is the MAC address of the individual station that originated the frame. Due to the possible role played by the AP, the SA is not necessarily the same equally the TA.

Destination Address (DA)—The DA is the MAC address of the final destination of the frame, and can also be a group or circulate also as an individual station. Once more, due to the AP(s), this accost might not match the RA.

The coaction amidst these accost types and the meaning of the two DS flags for data frames is shown in Tabular array 3.iii.

Table 3.3. DS Bits and Wireless LAN Data Frame Address Fields

Type of Network From DS To DS Address 1 Address ii Address 3 Address 4
Advert hoc (IBSS) 0 0 DA (= RA) SA BSSID N/A
To AP 0 1 RA (= BSSID) SA DA N/A
From AP 1 0 DA (= RA) BSSID SA N/A
ESS (multiple APs) 1 1 RA TA DA SA

A expect back at Figures 3.half dozen and 3.seven will show that these address patterns are reflected in the screen captures. The terminal two bits of the frame control flags are the DS bits, which are 01 (To AP) and 10 (From AP), respectively. The Proxima AP is passing the frame between the Cisco and Farallon wireless stations.

The Accost 4 field appears just when there are multiple APs. Normally, data frames in a elementary BSS with AP use DS bit combinations 01 and x to make their way through the AP from i wireless station to some other.

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Cloud Infrastructure as a Service

Stephen R. Smoot , Nam K. Tan , in Individual Cloud Computing, 2012

VNTag

The VNTag is a 6-byte Ethernet tag inserted into the Ethernet frame immediately after the destination and source MAC accost pair (MAC-DA and MAC-SA). Traditional Ethernet switches do not support the forwarding of frames where the source and destination MAC are on the same port, thus they do not forward frames between two VMs connected on the same switch port. VNTag resolves this issue by creating a virtual Ethernet (vEth) interface for each VM on the switch.

Notation:

The IEEE MACsec (authentication and encryption) tag tin can precede the VNTag.

In other words, the VNTag binds a vNIC to a vEth interface and the reverse applies too. A "VNTag-enlightened" switch is capable of forwarding between vEth interfaces then frames are forwarded between VMs continued on the same physical port. These VMs are identified past the destination virtual interface identifier (dst_vif [xiv bits]) and source virtual interface identifier (src_vif [12 $.25]) fields in the VNTag. The implementation of VNTag tin can exist done either as a VNTag-capable NIC or in the software by the hypervisor. Information technology can also be implemented as a separate box ordinarily referred every bit a fabric extender that acts as a remote multiplexer toward an Ethernet switch. Effigy 8.three illustrates 2 fabric extenders connected to two Ethernet switches. Each material extender has 4 × 10GE uplinks to the Ethernet switches and 48 × 1GE downwards-facing ports toward the servers. The uplinks from the fabric extenders to the Ethernet switches use the VNTag header, and 48 virtual interfaces (vifs) are used to identify each down-facing 1GE port.

Effigy 8.3. Fabric extenders

Note:

Palo, a CNA developed past Cisco, supports VNTag.

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Cisco IOS and IOS-XR Quality-of-Service Implementation for Carrier Ethernet and Virtual Leased-Line Services

Vinod Joseph , Brett Chapman , in Deploying QoS for Cisco IP and Side by side Generation Networks, 2009

9.6 Virtual Leased-Line Service

VLL services are point-to-point services for the wagon of mutual Layer 2 protocols such equally Ethernet, Frame Relay, Asynchronous Transfer Way (ATM), Point to Point Protocol (PPP), and High Level Data Link Control (HDLC). Each of these link layer protocols are in ubiquitous utilize in global data and vox advice systems. In an endeavor to provide a common transport for these protocols, a serial of IETF RFCs was developed to encapsulate them in MPLS Label packets. This encapsulation is commonly referred to every bit the Martini Encapsulation, after Luca Martini, the original author.

From a QoS perspective, each of these protocols requires a particular service level. For example, ATM can be deployed in one of five modes: Constant Bit Rate (CBR), Real-time Variable Fleck Rate (RT-VBR), Non-Real-fourth dimension Variable Flake Charge per unit (NRT-VBR), Available Bit Rate (ABR), and Unspecified Bit Charge per unit (UBR). Each of these modes requires a different treatment, both at the border and on the core of an MPLS network.

In general, these link layer protocols have the QoS attribute tolerances shown in Tabular array 9.iv.

Table 9.four. Virtual Leased-Line Protocol QoS Attributes

Link Layer Protocol Filibuster Jitter Loss
HDLC/PPP Low Low Depression
Frame Relay Medium Medium Medium
ATM CBR Low Low Low
ATM RT-VBR Medium Depression Depression
ATM NRT-VBR Medium Medium Medium
ATM ABR Medium Loftier Loftier
ATM UBR High High High
Ethernet Low Medium Medium

Note that Table nine.4 is non taking into business relationship the blazon of data beingness carried in each of the link layer protocols and assumes that the right service blazon is used in the right context and can only be used as a general guide.

Service delineation on HDLC/PPP links is per physical link; Ethernet, Frame Relay, and ATM, however, have the ability to multiplex multiple services on a single physical interface. Cisco IOS provides a command-line interface to back up multiple subinterfaces on a single physical interface. A typical example of marking QoS at the edge is shown next. In the illustration, we notice that policy maps are attached to private subinterfaces for diverse encapsulation types. In our illustration, nosotros look at Ethernet, ATM, and Frame Relay encapsulation types, and each of them represent a Layer 2 indicate-to-point VPN.

Virtual Leased-Line Configuration

!

interface GigabitEthernet11/4

!

interface GigabitEthernet11/four.100

  encapsulation dot1Q 150

  xconnect 1.ane.one.1 100 encapsulation mpls

  service-policy input <policy-map)

!

!

interface Serial0

  encapsulation frame-relay

!

interface Serial0.1 indicate-to-indicate

  ip address 3.1.3.ane 255.255.255.0

  frame-relay interface-dlci 140

  service-policy input <policy-map)

!

interface ATM2/0

!

interface ATM2/0.1 point-to-point

  ip address one.i.0.xiii 255.255.255.0

  no ip directed-broadcast

  pvc 0/100

  service-policy input <policy-map)

!

Finish

More sample configurations follow to help the reader sympathize this concept in more particular. In our "ATM-over-MPLS Configuration" analogy, we create a policy map named ATMoMPLS with a policer to enforce a CIR and accordingly mark traffic with an MPLS Experimental value of 5. This policy map is farther attached to an ATM interface, which hosts an ATM-over-MPLS Layer 2 VPN.

ATM-over-MPLS Configuration

!

!

  class-map match-whatever ATMoMPLS

    friction match input-interface ATM6/0 ← All traffic on Main interface/Subinterface is matched

!

policy-map ATMoMPLS

  class ATMoMPLS ← Common policy for all traffic on interface/sub interfaces

    police cir 128000 bc 16000 be 16000

      conform-activity set-mpls-exp-transmit five

      exceed-activeness drop

!

interface ATM6/0

  service-policy input ATMoMPLS

  xconnect 192.168.ii.1 20000 encapsulation mpls

!

Stop

In our "EoMPLS Port-Based Configuration" illustration, a policy map named REALTIME-Ingress is created to marker all traffic with an MPLS Experimental value of v. This policy map is further attached to an Ethernet interface, which hosts an Ethernet-over-MPLS Layer ii VPN.

EoMPLS Port-Based Configuration

!

!

!

Mls qos

!

mls qos mark ignore port-trust

!

class-map match-any REALTIME-Ingress

    description ### Matching Any ###

    match whatever

!

policy-map REALTIME-Ingress

    class REALTIME-Ingress

      fix mpls experimental imposition five -------- Prepare MPLS EXP 5!

!

!

interface GigabitEthernet1/3

  description ### Link to CE – EWS Layer2 VPN Customer ###

  no ip address

  xconnect 3.3.iii.3 1001 encapsulation mpls

  service-policy input vocalisation-customer

!

End

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Interconnecting can Busses via an Ethernet Backbone

Jean-Luc Scharbarg , ... Christian Fraboul , in Fieldbus Systems and Their Applications 2005, 2006

4.2 The "one for i" strategy

The more straightforward encapsulation strategy is to put each global CAN frame in a separate Ethernet frame and to transmit information technology as soon every bit possible. The expected benefit is a minimal delay. This strategy has been evaluated by a Simulation model (queueing network implemented in QNAP2). We consider an Ethernet link at 100 Mbs and TB = 0.05 ms (considering a modern microprocessor). The non-CAN Ethernet traffic is equally distributed between frames of 500, 1000 and 1500 bytes. There are two traffic sources for each frame length, one generating twoscore   % of the corresponding traffic and the other one the remaining threescore   %. The curve n = 1 of figure 5 shows the results for the example application of table 1 and 2.

Fig. 5. Encapsulation strategies and Ethernet load

We notice that there are missed deadlines for CAN frames as soon as non-CAN Ethernet load is greater than or equal to 20 Mbs. When this load is 35 Mbs, four   % of CAN frames miss their borderline. Above 35 Mbs, the pct of temporal faults on Can frames increases dramatically.

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